Single host plant species may harbour more than one species of Peronospora – a case study on Peronospora infecting Plantag

The genus Peronospora is the largest genus of the oomycetes, fungus-like members of the kingdom Straminipila that also contains amoeboid (e.g., Leukarachnion) and plant-like (e.g., Laminaria) life forms. Peronospora species are obligate biotrophic plant pathogens, causing high economic losses in various crops and ornamentals, including Plantago species. Several species of Plantago are used as specialty crops and medicinal plants. In this study, Peronospora species parasitic on Plantago were investigated based on morphology and phylogenetic analyses using two nuclear (ITS, nrLSU) loci and one mitochondrial (cox2) locus. As a result of these investigations, 10 new species are added to the already known Peronospora species on Plantago. Interestingly, it was found that four independent species are parasitic to Plantago major, highlighting that the reliance on the host plant for pathogen determination can be misleading in Peronospora. Taking this into account, morphological and phylogenetic analyses should be conducted as a prerequisite for effective quarantine regulations and phytosanitary measures.